1. Field of the Invention
The present invention relates to a clinging sheet. The clinging sheet can be clung to an adherend having a smooth surface, such as a glass, a plastics, a metal and a coating surface, easily peeled therefrom without damaging the clinging sheet and the adherend or staining them, and clung repeatedly to the same adherend or other adherends. The clinging sheet can be used for a label, a sticker, a seal and the like.
2. Description of Related Art
A pressure sensitive adhesive is generally used as an adhesive for a label, a sticker, a seal and the like. But, the pressure sensitive adhesive layer formed in the label et. al. has large tackiness of the adhesive. Therefore, when there is an error in adhering the label et. al. on the adherend, the label et. al. can not be easily peeled and adhered again in a suitable position on the adherend. And when the label et. al. is peeled after long time adhesion, the adherend is damaged, the label et. al. is torn, or it needs a lot of work to remove the pressure sensitive adhesive remained on the adherend. Further, a part of the adhesive permeates into the adherend, so that stain and/or discoloration are generated. Once rubbish and/or dust adhere to the pressure sensitive adhesive layer, the pressure sensitive adhesive strength is easily decreased sharply, the rubbish and/or dust can not be easily removed by washing, and it is difficult to restore the pressure sensitive adhesive strength. It is desired that the rubbish and/or dust can be removed from the adhesive layer of the label et. al. by simple washing and the label et. al. can be adhered again to the adherend.
In order to resolve these problems of the label, the sticker and the seal having the pressure sensitive adhesive layer, the label et. al. having the adhesive layer, which does not comprise the pressure sensitive adhesive, is proposed. For example, the clinging sheet of Japanese Utility model Application Kokoku 6-21711 has a clinging layer consisting of a silicone rubber formed on a polyester film and the clinging sheet of Japanese Patent Application Kokai 8-1870 has a clinging layer consisting of a polyurethane elastomer formed on a base film. However, the clinging sheets can resolve some problems of the label et. al. having the pressure sensitive adhesive layer, but is not sufficiently satisfied with the solution of the problems in any use conditions.
When the clinging sheet of Japanese Utility model Application Kokoku 6-21711 having a clinging layer consisting of a silicone rubber is adhered on the glass, a reaction between the silicone rubber and a glass plate is caused with water in air after long time adhesion on the glass plate, and the both members were adhered strongly, so that the clinging sheet is not easily peeled. In peeling the clinging sheet against the adhesive strength, the silicone rubber is remained on the glass plate in many cases and the removal of the silicone rubber is much difficult. Further, the silicone rubber adsorbs rubbish and/or dust easily because of easy generation of static electricity and the rubber properties, the surface of the clinging layer is stained and the adhesive strength is easily decreased. And, the rubbish and/or dust adsorbed on the clinging layer is difficult to remove by washing, but easy in compared with the pressure sensitive adhesive layer. Furthermore, a low molecular weight silicone component contained in the silicone rubber permeates easily into the adherend, the adherend is stained in almost cases, and a surface energy of the adherend is decreased.
In the clinging sheet of Japanese Patent Application Kokai 8-1870 having a clinging layer consisting of a polyurethane elastomer, the stain of the adherend as described above in the silicone rubber is not generated, adsorption amount of the rubbish and/or dust is little, and the clinging property is easily recovered by washing. But, in the case of the specific kinds of plastic adherends, the clinging sheet is adhered strongly after long time adhesion and can not be easily peeled from the adherend. In particular, the problems generate in the adherend having comparative high surface energy, such as the adherends consisting of a polycarbonate resin, an acrylic resin, a vinyl chloride resin and the like. When the adherend is made of glass, the problems are not generated.